It’s paint protection film to protect against damage, like rock chips or unintended scratches. Ceramic coating is also protective but acts more as a hydrophobic agent to make the vehicle easier to clean.
You are correct about the sensor issue. I think as long as you have an expert detailer, any sensor interference can be avoided. I went over this carefully with my detailer prior to moving forward.
Not everyone applies coatings, I did it for peace of mind.